I finished up my last project last night and tried my hand at populating one of these boards. I needed to keep referencing an unused board so it might be a good idea to print a 2-sided blowup of one. I also wrote down which resistor values were which before removing them.
The IC was actually the easiest part to place because of it’s size. The other small parts tended to wander around getting into trouble. I removed and replaced one part at a time with the exception of the input diode finishing the IC side first…
…and then the 7135 side.
I still need to add a pos pad and wire it up to see if it survived the transplant but continuity and resistance values check out.
I’ll be mailing out the other test boards soon( Djozz gets one ’cause he asked nicely) and there are still 2 more left.
Your mind is certainly not diminishing as you get older Rufusbduck. You continue to amaze me to the point maybe I should not be amazed anymore and just expect you to do things. Very nice effort.
My motivation for this was purely selfish but my naturally generous disposition and being able to get someone else to do the work compelled me to offer them at large. IOW, I don’t care how many other people want them as long as I get some.
Nobody else has one yet but me. and I won’t be home to wire it up for another few days. We should know by the weekend(that is if I did it right). The boards that were requested before I left home will go in the mail in the next day or two, the others this weekend. Most are US bound but I’ve no idea how long it will take for a letter to Europe.
Nobody’s mentioned it yet but there’s no reason you couldn’t do a Zener mod to this and put an mtg-2 in a AAA Minimag. Not much point in it since although you can get the voltage you won’t get enough current from 10440’s to justify it but when has that stopped us.
Remember the easier you drive an LED, the lower it's Vf. The lower the Vf, the more power the AMC chips have to burn off.
EDIT: I think this is how it works:
With fresh cells (8.4V total) and driving an MT-G2 at 3A, the Vf is approximately 6.2V. This means the AMC chips are burning off (8.4-6.2)x3 or 6.6W of power. Or around 825mW per chip (8 380mA chips).
With fresh cells (8.4V total) and driving an MT-G2 at only 380mA, the Vf is approximately 5.2V. This means thew AMC chip is burning off (8.4-5.2)x0.38 or 1.2W of power.
Which kind of brings me back to the question of why are the 350/380 binned 7135 chips the ones primarily used? There are regulation chips with much higher initial current, so why so low that we have to have 8 to get 3A? Or more and more and more…what if we started with a 1A chip? A 2A chip?
It's a number of factors. The primary reasons are because the chips are cheap, small, easily dimmed, and operate down to low voltages. A lot of the higher current chips either can't be PWM'd properly (react too slowly to PWM signals - case in point was the PICColo), are too big, or operate at voltages too high for the applications we like to work with.
Sucks. I'm always looking for new parts but the efficiency of switching regulators is attractive. We just need to get them small enough.
I have some thoughts about minor changes but I’d like to hear back from the others and have those comments grouped in the thread. Looking good so far though.
